1. Field of the Invention
The present invention relates to mechanical manipulating devices. In particular, it relates to an actuator for a compact gripping implement intended primarily for robotic applications for grasping, holding and moving an object or workpiece, wherein the gripper is rotatable.
2. Description of the Prior Art
As shown in U.S. Pat. No. 3,815,479 (Thompson), compound motion actuators are known. The actuator disclosed by Thompson is a fluid actuator for producing simultaneously or separately both reciprocating and turning motions. It includes a rotary power device coupled to a reciprocal piston such that the piston rod connected to the piston has imparted thereto the reciprocal motion of the piston as well as the rotary motion of the rotary device. Although the piston is coaxially connected to the rotating gear of the rotary actuator, the invention requires a guide rod telescopically fitted into the hollow piston rod for controlling the rotation thereof and a housing for the rotary actuator which is located at one end of the power cylinder for containing the piston. Thus, the actuator is not as simple in construction, compact or symmetrical as possible.
U.S. Pat. No. 4,134,306 (Grotness et al.) discloses a rotary actuator for converting reciprocating motion to rotary motion. The disclosed actuator includes a bellows arrangement connected to a rack whereby expansion and contraction of the bellows causes linear movement of the rack, thereby imparting rotary movement to the pinion.
U.S. Pat. No. 3,377,799 (Geyer) discloses a rack and pinion for providing rotational movement to a shaft. However, this patent does not appear to show relative sliding movement between the teeth of the pinion and the teeth of the rack. Somewhat similarly, U.S. Pat. No. 3,429,195 (Bassoff) relates to a lead generating mechanism having a plurality of rack and pinion mechanisms for rotating a work spindle. Although the Bassoff patent discloses a work table which is designed for reciprocal movement in the direction of the arrow shown in FIG. 1, it does not appear that any of the individual rack and pinion members are slidably movable relative to one another.
U.S. Pat. No. 3,786,938 (Kirkham) discloses a reversing drive for a tool changer. The Kirkham patent does appear to disclose a pair of racks (FIG. 2) and a pair of pinions in the form of rotatable gears having teeth which mesh with the teeth of the racks and are slidably associated with the racks in response to the movement of a piston rod. The axially extending or elongated teeth of the unitary rack structure also function as an axial guide for the gears. However, the Kirkham patent does not disclose the combination of a piston/cylinder arrangement and rack and pinion mechanisms for the operation and positioning of a rotatably positionable gripper head, nor does it disclose a multimotion actuator having a combination cylinder/piston and rack and pinion arrangement, in which the rack is disposed between a pair of pistons, thereby providing for a more symmetrical, compact device.